COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

THE INCIDENT OCCURRED ON PIPELINE WV2VA (24"") JUST OUTSIDE THE LOST RIVER COMPRESSOR STATION. THIS LOCATION IS IN HARDY COUNTY, MATHIAS, WV, GPS COORDINATES 38.875, -78.859. AS PART OF THE TRANSCANADA WB EXPRESS PROJECT, AN INSTALLATION OF A STOPPLE FITTING WAS BEING COMPLETED BY THE CONTRACTOR (TD WILLIAMSON). THE ORIGINAL FITTING WAS INSTALLED IN 2017 . DURING THIS OPERATION, THE TD WILLIAMSON TECHNICIAN REMOVE THE COMPLETION PLUG AND INSTALL THE STOPPLE/BYPASS. THE 24"" BLIND FLANGE WAS REMOVED AND THE FITTING SNIFFED FOR GAS. HE THEN INSTALLED A DEVICE /ADAPTER ONTO THE COMPLETION PLUG. THE STOPPLE VALVE ( SANDWICH VALVE) WAS INSTALLED. THE TAPPING MACHINE WAS THEN INSTALLED. THE TDW TECHNICIAN BEGAN TO HOOK UP HYDRAULIC UNIT TO THE TAPPING MACHINE TO PULL THE 24"" COMPLETION PLUG. HE BEGAN THE PROCESS OF REMOVING THE PLUG HE INFORMED THE TRANSCANADA AND BICON EMPLOYEES (PRIMARY CONTRACTOR) THAT HE NEEDED TO RESET THE MACHINE AND TO DO SO HE NEEDED TO BLOW DOWN THE GAS PRESSURE OFF THE MACHINE. HE THEN OPENED THE BLOW OFF VALVE AND BEGAN BLOWING DOWN, THE GAS BLEW THOUGH THE BLOWDOWN VALVE FOR A FEW SECONDS WITHOUT ANY SIGN OF DIMINISHING, THEN THE TOP BLEW OFF THE MACHINE AND ALLOWED FULL LINE PRESSURE TO ESCAPE TO THE OPEN ATMOSPHERE. THE EXHAUSTING GAS BLEW SEVERAL MACHINE PARTS OUT THE TOP OF THE MACHINE. NO INJURIES OCCURRED AND THE PIPELINE WAS ISOLATED BY MANUALLY CLOSING MAINLINE VALVES. THE AREA AT THE STOPPLE WAS CLEARED AS THE GAS WAS RELEASED. NO STRUCTURES (APPROX. 250')OR ROADS (APPROX. 175') WERE IN THE IMMEDIATE AREA. THE LOCAL FIRE DEPARTMENT RESPONDED, HELPING DIRECT VEHICLE TRAFFIC AND FIVE RESIDENCE WERE EVACUATED. THE INITIAL PIPELINE PRESSURE WAS 840 PSIG AND IS NOW BLOWN DOWN AND ISOLATED. THE MAOP IS 870 PSIG. A ROOT-CAUSE INVESTIGATING WAS JOINTLY CONDUCTED BY TRANSCANADA AND TD WILLIAMSON. IT WAS DETERMINED THE TD WILLIAMSON TECHNICIAN DID NOT PROPERLY FOLLOW THE PROCEDURE WHILE ATTEMPTING TO REMOVE THE COMPLETION PLUG. DURING THE INITIAL PLUG REMOVAL PROCESS, THE TECHNICIAN BECAME CONCERNED THAT THE RETRIEVAL WAS NOT GOING AS EXPECTED. THE TECHNICIAN ATTEMPTED TO RE-SET THE COMPLETION PLUG, IMPLEMENTED A STOP WORK, AND CONTACTED A TDW SME FOR GUIDANCE. WHILE THE TECHNICIAN RECEIVED GUIDANCE, HE DID NOT EFFECTIVELY COMMUNICATE THE FULL DEPTH AND BREADTH OF THE SITUATION. IT WAS LATER DETERMINED THAT WHILE ATTEMPTING TO REMOVE THE COMPLETION PLUG, THE PLUG HAD NOT BEEN FULLY REMOVED FROM ITS GROOVES AND HAD ONLY BEEN PARTIALLY RESET (WINGS NOT FULLY ENGAGED). AFTER RECEIVING GUIDANCE, THE TECHNICIAN DECIDED THE BEST COURSE OF ACTION WAS TO BLOW DOWN THE TAPPING MACHINE, REMOVE IT, AND INVESTIGATE THE PLUG EXTRACTION ASSEMBLY. AT THIS TIME, THE PRESSURE IN THE TAPPING MACHINE WAS EQUALIZED WITH PIPELINE PRESSURE AT 800-PSI. THE BLOWDOWN PROCEDURE CREATED A DIFFERENTIAL PRESSURE ACROSS THE COMPLETION PLUG. AS THE COMPLETION PLUG WINGS WERE NOT FULLY ENGAGED INTO THE PLUG FITTING GROOVES, THE DIFFERENTIAL PRESSURE ACTING ACROSS THE PARTIALLY SET COMPLETION PLUG, CAUSED IT TO BE RELEASED FROM ITS POSITION. THE COMPLETION PLUG THEN IMPACTED THE BORING BAR AND FORCED IT THROUGH THE TOP OF THE TAPPING MACHINE.